Beetles (Order Coleoptera)

There are more kinds of beetles than any other group of animals. Almost a third of all animal species are beetles. In Australia alone, almost 23 000 different species have been named, but there may be as many as 80 000 Australian beetle species. Beetles belong to the Order Coleoptera.

Beetles are one of the most easily recognised groups of insects, despite their remarkable diversity of colour and shape. Even young children are able to identify ladybeetles and christmas beetles.

Beetles are one of the most successful groups of organisms on the planet, occupying most habitats and taking advantage of many food sources. One of the major factors contributing to the success of beetles is their compact body design and in particular their tough protective front wings.

Thousands of Washing Beetles Phyllotocus rufipennis (Scarabaeidae) emerge in summer to feed on eucalypt blossoms but often mistakenly swarm on other white objects, such as drying washing, tennis players or even brides.

Adult Giant Pine Weevils, Eurhamphus fasciculatus (Curculionidae), congregate on the trunks of dying Hoop Pines (Araucaria cunninghamii) in south-east Queensland and north-eastern New South Wales. Their white, legless larvae feed on the inner bark of the same trees.

Piedish Beetles, Helea spp. (Tenebrionidae), are inhabitants of arid and semi-arid sand country. Their broad, oval shape, with an upturned edge all the way around, is thought to protect their legs from predators.

Larvae of cockchafer beetles like Rhopaea magnicornis (Scarabaeidae) are white curl-grubs that feed on plant roots. Large numbers of these adult beetles emerge from the ground after summer rains and fly backwards and forwards above lawns at dusk.

The most distinctive feature of beetles is their wing covers which are also called elytra. These covers are actually the thickened and hardened fore wings. The wing covers have lost their wing venation but often have closely spaced grooves or rows of punctures. Beetles use their more delicate hind wings for flying. When they are not being used they are folded beneath the wing covers which meet in a straight line down the back. Most beetles have wing covers that cover the whole of their abdomen. Some have shortened wing covers leaving one or often more segments of the abdomen exposed.

Most adult beetles are compact with a heavily armoured body. They usually have mouthparts with a strong pair of jaws designed for chewing. Take care if you try to pick up a large longhorned beetle, their powerful jaws can deliver a painful bite.

Beetle larvae come in as many varied shapes and sizes as the adults. Sometimes there is no easy way to tell if a particular larva belongs to a beetle. Many are grub-like with a soft body but most have a well-developed, armoured head. Most have three pairs of jointed legs on the thorax, but in some groups like weevils, there are no legs at all. Some beetle larvae look very similar to the caterpillars of moths and butterflies, but they do not have fleshy false legs on the abdomen.

The jaws of the Poinciana Longicorn, Agrianome spinicollis (Cerambycidae), are large and sharp.

A stag beetle, Lamprima latreillei (Lucanidae), clearly showing the line down the middle of the back where the wing covers meet.

The wing covers of beetles are actually their forewings. They lack wing veins but often have many parallel grooves or rows of punctures like this rare darkling beetle, Axynaon championi (Tenebrionidae), from arid Queensland.

Many beetles like this Fiddler Beetle, Eupoecila australasiae (Scarabaeidae), have bright, glossy colours.

Some of the most commonly encountered beetle larvae are the white 'curl grubs' of scarab beetles such as this larva of the Rhinocerus beetle, Xylotrupes ulysses.

Beetles are found in almost every imaginable habitat on land. Many species have also invaded freshwater.

Many beetles feed on living plants as adults or larvae, or both. Some, like leaf beetles, feed on the outside of plants, munching on the leaves or flowers. Other plant feeders are concealed, especially as larvae, boring inside fruit, seeds, stems or wood. Other beetle species feed on plant matter, but only after it has been broken down by other organisms such as fungi. Numerous groups of beetles are also specialised to feed on the fungi themselves.

Other beetles are predators, usually feeding on a range of insects and other small invertebrates. But some are more specialised. For example, some ground beetles have special jaws designed to capture and hold slippery, slimy prey such as snails and earthworms.

Beetles can be of great economic importance with many species attacking crops, destroying timber and invading our stored food. Others are beneficial, consuming insect pests or weedy plants. In contrast, beetles are of little importance in transmitting diseases of humans and animals.

Beetles undergo abrupt metamorphosis and pass through a larval and pupal stage before transforming into winged adults.

Variable Lady Beetle Coelophora inaequalis larva.

Variable Lady Beetle Coelophora inaequalis pupae.

Like other beetles, the Variable Lady Beetle Coelophora inaequalis (Coccinellidae), passes through larval and pupal stages before emerging as an adult (see three images above). The adults and larvae of lady beetles are beneficial predators of aphids and other sap-sucking insects.

Most lady beetles are beneficial predators, but the larvae (top) and adults (above) of the Twenty Eight Spotted Lady Beetle, Henosepilachna vigintioctopunctata (Coccinellidae), eat the leaves of tomatoes, potatoes and related plants.

The rainforest dwelling Snail-eating Carabid, Pamborus alternans (Carabidae), feeds on snails and earthworms, which it grips with specialised jaws. It can squirt a pungent, burning fluid from the rear when handled.

Fireflies, such as Atyphella scintillans, are actually beetles. This species is found in moist forests in south-east Queensland and north-east New South Wales. The winged males (3 in foreground) flash lights at the tip of their abdomens to signal wingless females (in background) on the ground.

When handled roughly, the day-flying Long-nosed Lycid Beetle, Porrostoma rhipidium (Lycidae), exudes a toxic milky fluid from the leg joints. The bold colours of these beetles advertise they are distasteful. Many other harmless insects mimic these beetles such as the moth Cyana meyricki (Arctiidae).